Conventionally, as the electrostatic precipitator of this type, the following apparatus has been known, and referring to FIG. 5 that is a front view showing the conventional electrostatic precipitator, a description will be given thereto (for example, refer to Patent Document 1).
As shown in FIG. 5, the electrostatic precipitator is provided with ground electrode plate 101 having a plate shape that is disposed in parallel with an air flow, and is also provided with discharge electrode 104 composed of supporting member 102 and a plurality of needle-shaped electrodes 103, which is disposed in parallel therewith.
By supplying a DC high voltage to discharge electrode 104 from a DC high voltage power supply, a corona discharge is generated between ground electrode plate 101 and discharge electrode 104 so that suspended particulate matters in the air are charged and collected.
The material for ground electrode plate 101 is metal, such as steel, stainless steel and aluminum. Moreover, as the material for needle-shaped electrodes 103, normally steel, stainless steel, or the like may be used; however, by taking into consideration a corrosive property and a corrosion resistant property, metals, such as titanium, iridium, platinum, rhodium and tungsten, or alloys of these may be used in some cases.
In this case, the electrode-to-electrode distance between ground electrode plate 101 and needle-shaped electrodes 103 of discharge electrode 104 is set to 30 mm, and an applied voltage to needle-shaped electrodes 103 is set to 18 kV.
In such a conventional electrostatic precipitator, when the electrode-to-electrode distance between ground electrode plate 101 and needle-shaped electrodes 103 of discharge electrode 104 is made too narrow, a spark discharge frequently occurs, resulting in a problem that an inherent dust collecting performance of the electrostatic precipitator is no longer obtained. Although this problem can be solved when the electrode-to-electrode distance is widened, the widened distance causes a reduction in a corona discharge quantity of the entire electrostatic precipitator, resulting in degradation of the dust collecting performance of the electrostatic precipitator.
In the conventional electrostatic precipitator, the electrode-to-electrode distance is widened to a distance (for example, 30 mm as described above) that no longer causes a spark discharge frequently. For this reason, since the corona discharge quantity from discharge electrode 104 becomes smaller, a plurality of discharge electrodes 104 are disposed in a direction of an air flow so that an attempt is made to ensure a sufficient corona discharge quantity so as to maintain a sufficient dust collecting performance.
Moreover, in accordance with this structure, plate-shaped ground electrode plate 101 also becomes larger in the direction of the air flow. Consequently, the apparatus as a whole becomes bulky in the direction of the air flow. The resulting problem is that, upon installation in a factory or the like, in the case of the installation on a floor, no margin space is sufficiently prepared because of various machine facilities placed therein, and in the case of the installation on a semi-second floor or a ceiling, it is difficult to ensure a sufficient space, because ducts for normal ventilation, air conditioning machines, cranes, illuminating devices, and the like are installed thereon.